regulator for electrical discharges



, June 7 1927. 1,631,626

w. D. coounea REGULATOR FOR ELECTRICAL DISCHARGES Filed Jan. 30, 1923 2 Sheets-Sheet Fig. 1., 4 Z 5 a 23%? i A 50 /a' Wis /a 7w ,./4'

William DCQ Iidge,

Hi5 Attorney Patented June 7, 1927.

UNITED STATES PATENT OFFICE.

WILLIAM D. COOLIDGE, OF SCHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELEG- TRIC COMPANY, A CORPORATION OI NEW YORK.

REGULATOR FOR ELECTRICAL nisonAReEs.

' Application filed January so, 1923. Serial no. 615,953.

The present invention relatesto regulation of the current in electric apparatus, and in particular to the regulation of current value in incandescent cathode vacuum tubes.

My invention is particularly applicable to the operation of thermionic devices by current derived from ordinary powercircuits which are subject to considerable. voltage fluctuation, altho its benefits are not confined to such operation.

In accordance with my invention the current in an'X-ray tube, or other electrical discharge device, is regulated by the intermediary ot a second electrical discharge de vice which is responsive to a magnified degree to current variations to be regulated and which controls the current-carrying capacity of the device to be regulated so as to maintain a substantially predetermined current value. A substantially constant current maybe maintained in accordance with my invention without moving parts orother complications and with a small expenditure of energy.

In the accompanying drawings, Fig. 1 illustrates an X-ray system adapted for opcration with substantially constant current from a source of variable voltage; Fig. 2 illustrates a similar constant current system with some modification of connections; Fig. 3 illustrates a more highly developed system;

and Fig. 4 illustrates a system containing a modified transformer arrangement.

The X-ray device 2 of Fig. 1 operates substantially by pure electron conduction, as described in my prior Patent 1,203,495 of October 31, 1916, and contains a cathode 8 and an anode 4 connected by the conductors 5, (3 to the secondary winding of a transformer. 7. The primary of this transformer is connected by the conductors 8, 9 to current distributionlines 10, 11. The cathode 3 comprises in addition to the cylindrical member shown in the drawing, a heated filamentary member (not shown) which is supplied with heating current by the conductors 12, 13 con nected to the secondary of atransiormer 1 1 in series with a regulable resistance 15. The cathode of the X-ray tube is operated at saturation current, that is, the impressed voltage is high enough to utilize substantial- 1;; all of the available electrons emittedv by the cathode.

A second electron discharge device 17 is provided. also comprising an incandescent cathode l8 and, an anode 19 contained within an exhausted envelope. The temperature of the cathode l8 varies with variations of current in the circuit of the X-ray tube, for

' example, by being connected as shown to the primary of a step-down transformer 20, the primary of which. is connected in series with the secondary of the transformer 7 by the conductors 21, 22. In Fig. 1 these conductors 21. secondary winding but if taps to this part of the transformer are not readily available, a connection as shown in Fig. 2 may be used in which the primary winding of the filament heating transformer 20 is connected in circuit with the high tension conductor to one of the outer terminals of the secondary of the transformer 7. The transformer preferably has a magnetic core containing an air gap as shown in Fig. 4 to get the most favorable phase relations.

In the system shown in Fig. 1 the electrodes 18, 19 are supplied with operating current by connection to the secondary ot a transformer 23, the primary of which derives current from the mains 10, 11, through the conductors 24, in series with an impedance device 26. In Fig. 1 the conductors 24, 25 are connected directly to the mains 10, 11,

whereas in Fig. 2 these conductors are connected to the cathode conductors 12, 13. In this case the transformer 20 and connected parts are at cathode potential and therefore, are insulated from lines 10, 11 by the trans former 14.

The temperature of the cathode 18 of the device 17 is so adjusted with respect to the impressed plate voltage furnished by trans former 23 that a saturation current is obtained. In other words, the applied voltage and thecathodetemperature are so chosen that substantially all of the available electrons from the cathode are carried to the anode. "llhisadj ustment of cathode tempera ture can he carried out by properly proper are connected into the center of the tioning the voltage of the secondary of the transformer 20 to the resistance of the cathode 18.

When the current in the X-ray tube circuitrises above or falls below the predetermined vailuefthe corresponding change of heating current in the filament 18 produces a magnified change of space current to the anode 19. At-saturation, the current from an lncandescent cathode \vames =11] accord ance with Richardsons equation.

current, may increase the "space current through the tubeasmuc-h as 800%.

i This rapid variat on of current Withdrawn I fromtheflines 10, .11 produces an accom- .panying'large change ,in voltage drop in an impedance'device .26, which may he 'cons'tituted'hy an iron Wire ballast inhydrogen or Jbyareactance. The impedance or voltageconsum-mgkdevlce' 26 ,1s connected inseries vrelationto the regulator tube .17 through the intermediary of the transformer-J23. Current drawn by the tube l7 varies a the voltage drop in the impedance .26, and hence modi- -fied'the voltage .otthe' heating circuit 12,- 13

throughthe intermediary otthe transformer 14:. .A vdecrease of voltage at 'thejterniinals of the-primary of. the {transformer 14: reduces the voltage of the cathodeheating current and hence reducesthe cathode temperature OfJthcj'deviceQ; a converse process an incipient fall. of; current through 'theX-ray tubedecrcases the currentcarrying capacity oi the vacuiunl tnbelf, hence decreases the current in; the impedance 26, decreases the wiltage drop and increases the "temperature the cathode in the X-ray tube. As either a rise or fall of current-is immediately counteracted' by a change in cathode temperature I of the X raytube,'thefcurrent cannot depart to an appreciable extent from a'predetermined value, y e p The system shown "in Fig. '3 has certain advantages when Wide fluctuations oflvoltage ofthe supply current occurs. For ex- 'a1'nple,lnit a single adjustmentis required to get regulation over a widc range. of X-ray tube load. In this system I have provided. a second electron regulator havingia main or plate circuit .31, "32' connected across the secondary oi the transformer in parallel with the devicel7. Thecathode heating circuit 8'3, 34 of second tube derives cur rent through "transformer 35 from the with a regulating resistance 4%. fprlmary :W1nd1ng'45 is provided for receiv mg current by the-conductors 46, 47 in 'cin mains 10, 11in series-with an impedance SG. A rise of voltage in the mains 1.0, 11 raises the voltage of the heating current of the cathode in the device 30, thereby producing in an amplified degree an increase of space current whichv being drawn from the mains '10, "11 will "increase the voltage drop in the viinpedances 36, 37, and thereby lower .the voltage of .the current drawnihyatlietrans- ,fonmer 114K017 heating the cathode of the X-ray tube 2. The size of the impedance 36 isch-osen-with respect to the variations of p voltage in theheating current. for the cathode ofth'e device 30-to vary the temperature and .hence the electron (or space) current suflieiently to produce such added potential I drop that the potentialatth'e terminals of the conductors '38,?39 would be substantially constaut,' if there wereno variationso'f cur changes in the X-raytube.

\Vhen internal changes in the "X-ray tube 2 occur, caused for example, someevolutlon of gas fromthe anode, or other metal part, or by the aging ofthecathotle during v use, orzany other reaso'nythenqthe consequent change .in space currentthrough theX-ray tube will vary the currentcarrying capacity of ithe device 17, thereby producing the .proper correctivechange in cathode temper atureto restore the current to substantially the original desired value. A resistance 40 .rmay' be providedto tleterminethe current rent in "the devicel'7 caused b internal through the lX-ray tube. *By-adiusting this variableresistance device140 the load cur rentof theX-ray tube may be set at a desired value and the regulator will maintain 'this current value substantially'constant in spite of internal changes in the vacuum-tube or-voltage changes inthe sup ly dine.

l esth'e spa ce current through as an X-ray 'tube is relatively small and i the a device such -voltage-is ery hig'ha liiglrratio of primary heating purposesl To reduce the number of primary turnsa separate "primary Winding "ovided to fl u'n ish .the greater part lyi f oi" the heating current, the variable current tmsecondziry turns in*thetransformer 20 is requiredtostep this high: "voltage cnerg of sina'llclu'rent v'ahie-to' a lowvoltagecurrent of greater amperage suitable for afilament lll.

component beingiurnished by anothcrpri- 1nary'u-indingjreceiving current proportional to-space current in the) tlcvice being regu- 4 the 'filamentot the regulating electron tlischarge device is sflppll ed jvltllcurrent il rom a secondary Winding at]. (it the r t v mary Wll1'(l1l1'g""l3 receives current ltroni "the llnes 10, *l l by the conductors 49, 50 in series A second till cnjit with the secondary wijudiugol the main transformer T'and hence also witl'rtho ray tube 2. i i f 3 ln ace-pending application,Serial No. tllfallt fl, liled (it)luj'lll'l'tlll ly herewitlu'l have made srcuerie claims on the regulation ol line voi'iditions by an electr-r'm discharge used in conjunction with a voltage consiuning device. t l hill} I claim as new and i'lesii'e to secure by Letters Patent oi the lluited Slater-axis:

l. 'lhe method of controlling the current value ot an electron discharge which con sists iu-produrine an .iiulepei'uleul; electron disehare'e; varying; the (airrent-carryingr capacity ot said seconiil ilischargre in accordance with the variatioiuy of current to be re gn lair-d, producing a s-iuhstautialdrop of voltage by d second disclr rgre proportioiuiil to! he current value thereof, 1 l varying], the elei'rtroug5eneration at the cathode of said lirsl i lischarue inversely with said voltage drop. i

' lhe iuetl'iod of regulating a varying;

electrical condition in a circuit which cou-- s in producing, independently an electron discharge at saturation current, varying the electron emissivity of the cathode of said discharge in accordance with variations of the condition to be regulated, producing a drop of voltage by said discharge proportional to the current value thereof, and regulating said varying condition inversely with voltage variations in said second circuit.

3. The method of regulating the space or electron current in a vacuum tube having an incandescent cathode supplied with current ol variable potential, which consistsiin adjueting, the temperature ot the cathode of said tube with respect to the appliedvoltage to produce saturation current, producing a SBQOHtlQlQCtIOl] discharge, varying the second discharge in response to thevariatioiis ol space current of the first discharge, and

controlling, the temperature oil the cathode in the tube being'regulated inversely as a function of current variations of the seconddischarge.

4. The method of regulating the current in an X-ray device whico consists in produeling an electron discharge at saturation current in an independent circuit, varying the gei'ieration of electrons supporting said discl'iarge in accordance with current variationsiin said X-ray device, producing a drop of voltage by said discharge, and regulating the current inthe X-ray devicein accordance with voltage *ariations in said secondcircuit. i

5. The method of operating an X-ray'tube having an incandescent cathode supplied with current of variable voltage which con sists in producing a second electrical discharge, varying the current valuecf said second discharge directly in response to variations'of current in said X ray tube, producing a voltage drop externally to said second diuehar 'e, varyiiu; in accordance with the current ol said discl'uu'ge, and controlline the ternpcrature ol' said X-rav cathode in acmrdanre with the dill'erencc hetwecu the variable voltage ol' the t't lliode heating circuit and the voltage drop noducetl by said second dii'uihargrc.

(S; The method of regulating); the t-J I HICQ current in aueloclron i'lisclia' o device containing an ineau'ilei-scout cathode and an anode which cousis s in heating said cathode at incaudescence, coui'luctinp; an electron current between said electrodes at a voltage .iuaterially above the voltage nev ry to produce a saturathm current, lll'th'llli'lllg a second.electron discharge at the saturation ci'irreul. value, varyingr the emission oi said second i'lii'ichar in response to the variation ol the currci'it ol the lirst discharge, and varyii'ig the euiissioi'i ol the lirst discl'iarg e iuversi-ily with respect to the current of the second iliscl'iurge.

7. An electric system ol' distriluition (3011M prising, a circuit one of the electrical conditions of which is subject to variation, a second circuit, an electron discharge device in said second circuit, means for varying the currenbcarryiug capacity of the device in said second circuit in accordance with the varying; condition to be regulated, means for producing a s hstantial drop 01" voltage varying with the current output of said discharge device, and means for regalataing; the electrical condition subject to variation inversely withsaid voltage drop.

8. An X-ray s cm comprising an Xray tube, a source of Cllll'eflt connected thereto, a second circuit, a. thern'iionic device operated at saturation by current derived from said second circuit, means for varying the electronemission ol said device in accord ance with variations of current in said X.- ray tube, means for producing by said do vice a drop of voltage, and means {or vary ing the current carrying capacity oi. said X-ray tube in response tothe dill'cronce be tween the voltage in saidsecoed circuit; and said drop of voltage.

[9. An X-ray syston'i comprising, an electric distrsiln'itint, circuit, an. X-ray tube, translormer i'i'ieai'is for supplying said tube free said circuit, a volhi e-consuming means also supplied from said circuit, a thormionic device connected to derive current through sa'id'mea-ns, means for varying the c1n're1'1tcarryinc capacity of said device in response to the current value in said X-ray i ing circuit and the voltage drop in said consuming means, a second voltage consuming both saidthermiouic devices, and means for heating the cathode'otsaid X-ray tube by tributing circuit and the combined voltage V operated at saturation current,- and means current having a voltage proportionalwto the dlflerences between the voltage of-said dis-i dropin said voltage consuming means.

comprising a circuit carrying current one of the varying electric conditions of which is to be regulated,asecond circuit, a ther mionic discharge device flied by said second circuit, said device containing a cathode for varying the electron emission of said cathode in accordmice with the varying condition of the first circuit which is to be regulated,1neans for producing a drop of i I voltage-varying with the currenttravers V20 ing said discharge device, and means for regulating the varying electric condition of said first circuit in response to the voltage of said second circuit as modified by said voltage drop. j; i

11; The combination of twoelectron conduction devices, a space current circuit and an electrode heating circuit torieach of said respective devices, means for varying the current in one of said heating circuits directly 1n response to the current in the space circuit-0f theother dev1ce,'and means'for varying the heating current of the other electron device inversely with the current in the space. circuit of the first device.

12. Anelectric system comprising a source of electric energy, a. vacuum tube having electrodes at least one of Which, is adaptedsource, a seeond vacuum, tube containing electrodes one of which 18 adapted to be heated, means, for supplylng a saturation currenttosaid tube from said source, means for varying- "the electron emission in said second tube in response to space current variations of the :lirsttube, and means con, nected to the electrodcsbf the second tube for varying the heating current of said first tube inversely with the electron emission 1n thesecond tube, a V i 1;}; The vcon'iloination of a thermionic .d1s-' charge fdevi'ce, a second tl'iermionic, dis- I chargedevice, means torflyarying thecura rent carrying capacity of said second therinionic device in response toi variations of current value inv said first thermionie'lde -vice andineans'for regulatii' g thetemperatureof a tllQIlDlQIlIQ electrode in said first device through the intermediaryo'f current var at ons? in sa d second devic -l4gln comb nation wlth axthermionic X- ra'y tube, a thermionic regulator tube, means nnpedance.

,ttorrvarying the currentcarryingcapacity of said regulator tube 1n response tocurrent-variations in said X-ray tube, and means a for I regulating the temperature of the eathodeof said X-ray .t ubein response to current'variations o'f-said regulator tube 1 prising-an electrondischarge device having an incandescentcathode, a main supplycit? .15. Electrical discharge apparatus om- 10. An electr c system ofv distribution lorheating the'cathode of the second di-scharge device by current varying directly with current in said main supply c1rcuit,-a-I second supply circuit for said second "dis- 1, charge device, an impedance device in said second circuit, and means for, heating the cathode of the first discharge device by current having a voltageproportional to the 'dilterencebetween the voltage of said second the voltage drop said supply circuit and 16.,The combination of a thermionic de vice, a second thermionic device, means ,whereby' the electron current 1n the second device is varied directly withthe current in theffirst device, and means forvarying the electron current insaid firsum'entione'd electron device inversely withithe current traversing the second device. 7

17;. An X-ray apparatus comprising thecombination of an ;X'-.ray tube" having .a cathodeiadapted to emit electrons when heats ed by passage of current, a supply circuit connectedito the electrodes of said tube, a

regulator vacuum tube having an electroneniitting cathode adapted to be heated by passage of current, connections for heating said-cathode with currentwhich is proportional to the main load current of theX-x ray tube, a supply circuit for said regula tor tube, a voltage-consuming device in said supply circuit connected tomodify'the voltage of said circuit in response :to current suppliedto the regulator tube, and means. for heating thei'X-rny tube cathode by' cur-- v rent havlng a voltageproportionalto the modified voltage of said supply circuit.

18. The combination of a mainthermionic" discharge device in hich-a constantlcurrent carrying {capacity is desired, a regulate "ingthermionic device, a supply circuit for saidrcgulating device," means tortvary'ing thecurrent-carrying capacity of said reguu-i latlng device ln'response to Incipient vari'a:

tions 'oteurrent in said first device, means for producing in'said supply circuit a drop offvoltage proportional to a current travers ing said second device, a secondregulating therm onicdev ce, means forvary ng the currenticarrying capacity of the second regulating device in response i to voltage f va riations in the supplycireuit ofthefirst regulat ng, devic means for producing an added potential drop in-said snpplyleircuit proportional to current traversing the second regulating device and means for heating the cathode of the main discharge device of current having a voltage proportional to the modified voltage of said supply circuit.

19. The method of regulating the current in a thermionic discharge which consists in producing a second thermionic discharge, varying the current-carrying capacity of said second discharge in response to current 10 'variations in the discharge to be regulated and controlling the generation of electrons for supporting said first discharge through the intermediary of said second discharge.

In witnesswhereof, I have hereunto set 15 my hand this 29th day of January, 1923.

WILLIAM D. COOLIDGE. 

